Range: S. China, Japan, and India. It is present in the provinces of Ontario and Quebec in Canada, and in most of the eastern and central states from Massachusetts and New York in the northeast, west to Minnesota and south through the Great Plains to Texas and east to extreme northern Florida in the United States

Physical Description

With stems that are typically decumbent, meaning that they are prostrate at the base but become erect towards the tips, but some individuals may be simply erect. The diffusely branched stems tend to root at the basal nodes. The pubescence on the stems is variable, but common patterns include a line of hair continuous with the leaf sheath, or they may be glabrous basally, meaning hairless, and puberulent towards the extremities, that is covered with fine hairs. The leaves are sessile: they lack a leafstalk, also known as a petiole; or they may be subpetiolate, meaning they have very small petioles. The leaf sheaths are cylindrical, sometimes striped with red, and typically glabrous, but usually have margins that are puberulent or pilose, meaning lined with fine, soft hairs. The leaf blades range from narrowly lanceolate, or lance-shaped, to ovate-elliptic, between egg-shaped and ellipse-shaped. They measure 3–12 cm (1–4½ in) by 1–4 cm (½–1½ in) wide. The blades range from glabrous to puberulent and have scabrescent, or slightly rough, margins. Their tips are acute, meaning they come to a point quickly, to acuminate, meaning the point develops gradually. The leaf bases are oblique, or uneven.The flowers are arranged on inflorescences called cincinni (singular: cincinnus), which are also called scorpioid cymes. This is a form of a monochasium where the lateral branches arise alternately. The cincinni are subtended by a spathe, a modified leaf. The solitary spathes usually measure 1.2–3 cm long (½–1¼ in), but some may be up to 3.5 cm (1½ in) in length, while they are 0.8–1.3 cm (¼–½ in) tall, but sometimes up to 1.8 cm (¾ in). The uncurved spathes typically have a cordate, or heart-shaped, whitish base, which contrasts with its dark green veins. Their margins lack hairs, are somewhat scabrous, or rough, and are unfused, meaning they are distinct to the base. Their apices are acute to acuminate while the surfaces are glabrous, puberulent, or hirsute-ciliate, meaning with longer, shaggier hairs. The spathes are borne on peduncles, or stalks, that measure 0.8–3.5 cm (¼–1½ in) and sometimes up to 5 cm (2 in) long.

There are often two cincinni present, though the upper, or distal, cincinnus may be vestigial. The lower, or proximal, cincinnus bears 1 to 4 bisexual flowers and is nearly included in the spathe, while the upper cincinnus has 1 to 2 male flowers and is about 8 mm (0.3 in) long. The individual flowers are subtended by bracteoles that fall off early in development. The pedicels supporting single flowers, and later the fruits, are erect initially but curve when in fruit. They measure about 3–4 mm (0.11–0.16 in). The 3 concave, membranous sepals are inconspicuous, but persist after the fruit develops; the lateral pair are fused basally, measure only 4.5–5 mm (0.18–0.2 in) long by 3–3.7 mm (0.11–0.15 in) wide, and are elliptic and glabrous. The lower sepal is lanceolate and about 4.5 mm (0.18 in) long by about 2.2 mm (0.09 in) wide. The 2 upper petals are blue to indigo in colour, while the much smaller lower petal is white. The upper two petals measure 9–10 mm (0.35–0.39 in) long by 8–10 mm (0.31–0.39 in) wide, while the lower petal is 5–6 mm (0.2–0.24 in) long by about 6 mm (0.24 in) wide. The 2 upper petals are composed of a claw about 3 mm (0.11 in) long and a broadly ovate limb with an acuteapex and a cuneate-cordate base.

There are three anticous fertile stamens, meaning they are on the lower part of the flower, and three posticous infertile stamens, meaning they are on the upper part of the flower. These infertile stamens are termed staminodes. The fertile stamens are dimorphic: the lateral pair have maroon to indigo anthers that measure about 2 mm (0.8 in) long and are elliptic with a base that is sagittate or arrowhead-shaped. Their filaments are about 10–12 mm (0.39–0.47 in) long. The central fertile stamen has a yellow, ellipticanther with a maroon connective and a base that is hastate or spearhead-shaped, but with the lobes at right angles. The anther measures about 2.5 mm (0.1 in) long while its filament is about 5–6 mm (0.2–0.24 in) long. The three staminodes are all alike with yellow, cruciform, or cross-shaped, antherodes that are about 2 mm (0.08 in) long on filaments about 3 mm (0.12 in) long. Sometimes the antherodes will have a central maroon spot. Each antherode has two abortive lateral pollen sacks. The ovary is ellipsoid, about 2 mm (0.08 in) long and has a style that is about 1.3 cm (0.51 in) long.

The fruit is a dehiscent, ellipsoid capsule with two locules each containing two seeds. The capsule is glabrous, brown, measures 4.5–8 mm (0.18–0.31 in) long, and dehisces into two valves. The seeds are brown or brownish yellow in colour and deltoid, or roughly triangular in outline. They are dorsiventral, meaning they have distinct upper and lower surfaces, with the ventral, or lower, surface being planar and the dorsal, or upper, surface being convex. Seeds range in length from 2.5–4.2 mm (0.1–0.16 in), but seeds as short as 2 cm (0.08 in) can occur, while they are 2.2–3 mm (0.09–0.12 in) across. The surfaces are rugose pitted-reticulate and are densely covered with smaller farinose granules with sparse larger farinose granules

The leaves are depurative, diuretic, and febrifuge. Used as a throat gargle to relieve sore throats and tonsillitis. A decoction of the dried plant is used to treat bleeding, diarrhea, fever etc.Leaves, flowers and young shoots - raw or cooked. Chopped finely and added to salads or cooked as a potherb. A sweet taste with a mucilaginous textureA bright blue dye is obtained from the petals. In Japan there is a sizeable dye industry devoted to the plant